Such a catheter has been described in applicant's Dutch patent application 1003033. The catheter described in said patent application is used as inner catheter fitted inside a guide catheter. The guide catheter is provided with first signal transmission means and the inner catheter is provided with second signal transmission means, which all extend between the proximal end and the distal end of the catheter system. At the distal end the first and second signal transmission means connect to each other in order to allow signal transmission to take place between the first and the second signal transmission means. The object of this system is to make it possible to determine the position of the inner catheter.
The aim of both the present invention and the above-mentioned Dutch patent application 1003033 is to solve the problem of there being no fixed relation between the angular position of the distal end of the catheter, that is the end of the catheter which is inside the patient, and the angular position of the proximal end of the catheter, where the catheter is controlled by rotation. It is therefore the objective of the invention to provide a catheter with which it is possible to reliably measure the angular position of the distal end.
To realize this, various proposals are already known from the prior art. The thesis "Scanning mechanisms for intravascular ultrasound imaging: a flexible approach" by H. ten Hof, 1993, ISBN 90-9006072-3, pp 120, 121, suggests as possibility an acoustic method applying acoustic measuring means which are placed in a perimeter and at a distance from each other, together with a noise source at the distal end of the catheter. Mention is also made of a capacitive measuring method wherein, dependent on the rotation of the catheter, a capacity adjustment of a capa city at the distal end takes place. A further suggestion is an electromagnetic method, wherein a micromotor is placed at the distal end for the adjustment of the catheter tip. Also mentioned is an optical reflection method wherein a code disc is used, provided with reflection lines, and positioned at the distal end of the catheter. However, all these known embodiments have proven to be unpractical, unworkable, or ineffective.
DE-A-3,435,369 does not relate to a catheter system but to an endoscope equipped with a polarization filter. The polarization filter serves to vary the illumination of an object to be observed with the aid of the endoscope such as to avoid over-adjustment of the video installation. The system disclosed in this publication is not equipped for the determination of the position of the catheter's distal end.